Abstract
We study analytically the existence of periodic solutions of the generalized Liénard differential equations of the form x¨+fx,x˙x˙+n2x+gx=ε2p1t+ε3p2t, where n∈N*, the functions f,g are of class C3,C4 in a neighborhood of the origin, respectively, the functions pi are of class C0, 2π−periodic in the variable t, with i=1,2, and ε is a small parameter as usual. The mathematical tool that we have used is the averaging theory of dynamical systems of second order.